FasL Expression in Articular Discs of Human Temporomandibular Joint and Association with Osteoarthrosis

Background Apoptosis is a programme of cell death which does not induce an inflammatory response. Recent previous research has suggested a correlation between temporomandibular internal derangement and apoptosis. Fas ligand (FasL) is an apoptosis‐inducing factor, known to trigger apoptosis through distinct signal pathways. This study aims to examine, by immunohistochemistry, the expression of FasL in temporomandibular joint (TMJ) articular discs of patients with anterior disc displacement with reduction (ADDwR) and without reduction (ADDwoR) in patients with and without osteoarthrosis (OA). Methods Forty‐two (n = 42) TMJ articular discs were divided into two cut‐offs: (i) 8 control, 17 ADDwR, 17 ADDwoR, and (ii) without OA (n = 25) and with OA (n = 17). The area of immunostaining was compared statistically between groups (P \u3c 0.05). Results Statistically significant differences were found in the expression of FasL in TMJ discs between the three groups (P = 0.001). ADDwR presented significant higher FasL expression when compared with ADDwoR (P \u3c 0.001). Significant higher FasL expression was observed in the group without OA (P = 0.001). All patients without OA presented ADDwR, while all the patients with OA presented ADDwoR. Conclusion A higher area of in situ immunostaining of FasL was found in temporomandibular discs with reduction, which is the less severe condition. Moreover, a reduced expression of FasL in the discs of patients with osteoarthrosis was found, suggesting that some aspects of apoptosis might underlie the progression of TMJ disorders